The invention concerns a device for the superplastic forming of a blank, in a moulding tool with a lower mould and an upper mould, into a component, in particular a suction component, with a three-dimensional geometry, wherein for purposes of forming, the blank can be subjected in the mould to pressure and temperature, and the blank has perforations in at least some regions.
For purposes of minimising the fuel consumption of aircraft, in particular of passenger aircraft, the objective is to maintain laminar flow as far as possible over the active aerodynamic surfaces. Such aerodynamic surfaces are, for example, the wings, horizontal tail unit, vertical tail unit, landing flaps, rudder, elevators, and other regions of the aircraft structure. This is because turbulent zones with vortices near the surface increase the drag of the aircraft significantly and impair the energy efficiency. However, not all structural regions of an aircraft can be designed such that the airflow has a laminar profile under all operating conditions.
In order to minimise vortices, in particular near the surface in the region of such active aerodynamic surfaces, suction devices can be deployed. The principle of removal by suction has already been of known art for several decades, wherein proof of function has undoubtedly been obtained. The major problem lies, however, in particular in what has been so far complex implementation in production terms, which still stands in the way of any widespread deployment of this technology in civil aviation. In the region of its relevant incident flow surface such a suction component possesses e.g. fine perforations, via which a proportion of the airflow is sucked off by means of a pumping unit, and by this means a local slightly reduced pressure is composed for purposes of reducing the turbulence. Such components require however an active aerodynamic surface with an extremely complex three-dimensional surface geometry, which in general can only be manufactured with difficulty. Here the superplastic forming method (SPF), which is of known art, but up to the present time is complex in production terms, is deployed in individual cases. In the superplastic forming method a component that is initially approximately plane is formed with the aid of a multi-part moulding tool and with the application of certain pressure and temperature parameters. The temperature to be applied can—depending on the metal or metal alloy to be formed—reach values of up to 1000° C. The forming pressure necessary for the superplastic forming process within the mould is preferably generated by means of a gas, or a noble gas. Here extensions in length of several 100% can be achieved relative to the dimensions of the initial material, wherein by virtue of the superplasticity no necking or cracking occurs and an even wall thickness is maintained. One disadvantage of the superplastic forming method lies in the fact that in order to build up a sufficient forming pressure the initial material must be impermeable to gas. From this it follows that for the manufacture of suction components with complex shapes by means of the superplastic forming processes of known art the perforations must be introduced at a later stage, which increases the complexity of the production process considerably.
DE 44 36 748 C1 shows a method for the superplastic forming of an internally stiffened hollow component with a wall in which at least some regions are perforated.
In this method the initial material to be formed in the course of a superplastic forming process already has perforations. In order nevertheless to be able to build up the necessary forming pressure in the mould, the holes of the perforations are temporarily covered during the forming process by means of a molybdenum foil. One disadvantage of the method lies in the fact that after completion of the forming process the molybdenum foil applied to the perforations must be chemically removed in a complex manner so as to ensure the air permeability of the micro-perforations of the formed suction component.